Process for producing synthetic chamois leather-like material having improved water absorbency and abrasion resistance

ABSTRACT

IMPROVED SYNTHETIC CHAMOIS-LIKE MATERIAL BY PROVIDING A WATER ABSORBENT NON-WOVEN TEXTILE FLEECE, IMPREGNATIN THE FLEECE AT LEAST ONCE WITH A LIQUID FORM A BINDER MATERIAL, AT LEAST PARTIALLY DRYING THE IMPREGNATED FLEECE WHEREBY CAUSING DEPOSITION OF THE IMPREGNATED BINDER MATERIAL AS LAMELLA PREDOMINANTLY AT THE CROSSING POINTS OF FIBERS WITHIN THE TEXTILE FLEECE, APPLYING TO BOTH MAJOR SURFACES OF THE BONDED FLEECE A LIQUID FORM COAGULATABLE RUBBER LATEX MATERIAL UNDER SUCH CONDITIONS THAT THE LATEX REMAINS ON THE SURFACE OR SUBSTANTIALLY ONLY AT THE SURFACE OF THE BONDED FLEECE, AND CAUSING THE RUBBER CONTENT OF THE COAGULATABLE LATEX TO COAGULATE BY HEATING THE COATED FLEECE TO ABOUT 40 TO 80*C. THE COAGULATED LATEX FORMS A DISCONTINUOUS PARTICULATE COATING ON THE SURFACE OF THE FLEECE WHICH SIGNIFICANTLY REDUCES PILLING.

United States Patent Oli-ce ABSTRACT OF THE DISCLOSURE Improved synthetic chamois-like material by providing a water absorbent non-woven textile fleece, impregnating the fleece at least once with a liquid form binder material, at least partially drying the impregnated fleece whereby causing deposition of the impregnated binder material as lamclla predominantly at the crossing points of fibers within the textile fleece, applying to both major surfaces of the bonded fleece a liquid form coagulatable rubber latex material under such conditions that the latex remains on the surface or substantially only at the surface of the bonded fleece, and causing the rubber content of the coagulatable latex to coagulate by heating the coated fleece to about 40 to 80 C. The coagulated latex forms a discontinuous particulate coating on the surface of the fleece which significantly reduces pilling.

This application is a continuation-in-part of application Ser. No. 800,043, filed Feb. 13, 1969, now abandoned and of application Ser. No. 513,524, filed Dec. 13, 1965, now abandoned.

As used in the instant specification, the term coagulation is to be distinguished from other forms of precipitation. Coagulation, as the term is used herein, means a rather sudden solidification or flocculation of material from a latex without necessarily removing the carrier liquid (solvent). Thus a latex can be coagulated such that the dispersed solid phase therein is caused to solidify and agglomerate without evaporating the liquid phase or drying the entire latex. This is to be distinguished from precipitation in the normal sense of the term which embraces the solidification of a solid component from a solution or latex by the reduction of solvent content and even by wholly drying. In precipitation, the solid material comes out of solution and solidifies in proportion to the relative proportions of the solvent and solute. Coagulation, on the other hand, causes solidification of the solute to about 100% extent substantially instantaneously without regard for the relative proportions of the solute and solvent.

It is known to produce synthetic chamois articles by providing a non-woven textile fabric and impregnating such with a suitable binder. There can be used one or more sequential impregnations, and there can be employed water soluble salts and other materials along with the impregnations or introduced at different times which can, after the impregnated binder is set up, be washed out so as to leave a larger proportion of voids in the final product, whereby increasing the porosity of the product without simultaneously significantly adversely affecting the strength physical properties thereof. It is further known to provide a latex or other coating material on the surface of such bonded, non-woven textiles in order to improve the surface characteristics thereof. The surface coating can be applied before or after the impregnation 3,592,685 Patented July 13, 1971 of binder and can be applied to one or both major sur faces of the textile fabric.

Bonding agents impregnated according to the prior art have been deposited within the fabric interstices from their liquid form impregnant composition by evaporating the carrier liquid (solvent), whereby depositing the binder as lamclla (see FIGS. 6, 7, and 9 of US. Pat. 2,719,795) at the intersecting points of the fiber content of the nonwoven fabric. Such lamclla deposition is considered to be most desirable within the body of the fabric since it effectively bonds adjacent fibers together while occupying only some of the interstitial space of the nonwoven fabric.

It is known that non-woven textile articles, particularly those having synthetic organic fibers, made according to the prior art techniques described immediately above, have a tendency to pill and that in order to reduce such pilling it has been necessary to decrease the surface porosity of such bonded non-woven fabrics to a significant extent.

In the prior art, the coatings which have been applied to the surfaces of such bonded non-woven fabrics to reduce pilling have been deposited from their liquid form coating compositions by evaporation of the solvent or liquid carrier in a manner substantially smaller or identical to the impregnation technique. The rubbery or resinous portions of the textile fabric as lamclla, principally at the intersecting points of adjacent fibers, bonding such adjacent intersecting fibers together and occupying some of the surface voids between fibers.

It is an object of this invention to provide a novel synthetic bonded, coated, non-woven fabric material having decreased pilling tendencies as compared to the prior art.

It is another object of this invention to provide an im proved synthetic chamois leatherlike article.

Other and additional objects of this invention will become apparent from a consideration of this entire specification, including the claims hereof.

In accord with, and fulfilling these objects, one aspect of this invention resides in a modification of existing bonded, coated, non-woven fabrics by internally bonding a non-woven fabric by known precipitation of binder techniques and by depositing a surface coating composition by coagulation rather than by precipitation as per the prior art, and by applying the surface coating only after internal bonding of a non-Woven textile material. The particular internal bonding agent or agents chosen and the particular surface coating agent or agents chosen may be per se known compositions.

According to this invention, improved pilling resistance is accomplished by producing bonded, coated, non-woven fabrics in this very special manner, whereby changing the surface characteristics of such material as compared to other synthetic chamois materials made according to the prior art.

Synthetic chamois is made according to this invention by the following sequence of steps:

(1) A non-woven fabric of suitably chosen continuous or staple length fibers is produced by conventional nonwoven fabric manufacturing techniques.

(2) This fabric may be optionally needled according to known techniques in order to increase its delamination resistance and transverse strength. i

(3) The needled or unneedled non-woven fabric has impregnated thereinto a conventional liquid form binding composition.

(4) The liquid carrier (solvent) material is evaporated, whereby depositing an impregnated binder as lamclla, joining intersecting adjacent fibers, principally at their crossing points.

Steps (3) and (4) can be repeated as many times as are desired to form a product having the desired physical properties.

(6) Applying to at least both major surfaces of the thus bonded textile non-woven fabric a liquid form coagulatable rubber latex composition in such manner and under such conditions that this liquid form coagulatable latex composition remains substantially on the surface upon which it is deposited.

(7) Coagulating the coagulatable rubber material from the latex by heating such latex to about 40 to 80 C.

(8) Removing any residual liquid to substantial dryness, and

(9) Vulcanizing the binder and/ or the coagulated rubber coating.

The vulcanization can be accomplished at one time, whereby all resinous and/or rubbery material is vulcanized together. Alternatively, vulcanization may be carried out at various times for the various resinous and/or rubbery materials supplied. Thus, for example the internal binder material can be vulcanized before the coa'gulatable coating is applied, or at the same time that the coagulated coating is vulcanized.

The bonded non-woven fabric described can have impregnated thereinto certain known water soluble salts for the purposes of increasing the porosity of the synthetic chamois product. This step is per se known in the art and can be carried out according to art recognized techniques.

If this salt impregnation and dissolution step is used,

the water soluble salts should be washed out of the bonded non-woven fabric either before or after the surface coating of coagulatable material is applied and the rubber coating material coagulated.

It should be understood that the preparation of the non-woven fabric is conventional, and the impregnation of this non-Woven fabric with internal binder is conventional. It should also be understood that the coagulatable latices used are themselves well-known materials and that no invention is claimed in any novel latex per se. The invention for which patent protection is here sought is the improvement engendered by the use of a coagulatable latex as a vehicle for coating non-woven textile fabrics, whereby making a synthetic chamois material, having improved pilling resistance.

The present invention resides in the discovery that, when the fleece material or fabric is provided in a final operation with a coagulated, porous, discontinuous elastic or resinous coating on both sides, the surface of the final product is substantially free of fibers and, consequently, cannot show any pilling phenomena. This surface, however, has not lost any significant portion of its porosity due to the coating thereof by the particular technique of this invention.

The coagulatable rubber dispersion coating material which is used to cover the surface of the fleece material as a finish, should preferably be introduced in a heatsensitive condition. On the addition of suitable compounds, such as polyvinylmethyl ether or polyhydroxypropylene glycol or certain siloxane compounds well known in the art, or their equivalents, the dispersion coagulates spontaneously during drying at a temperature of 4080 C., depending upon the proportion of these compounds that is used. Any material equivalent to such ethers, glycols and siloxanes may be used, providing they have the characteristic of solubility in cold water, but of becoming insoluble in Water at higher temperatures, and which coagulate and cause coagulation of the rubber or resinous particles of the dispersion or equivalent coating medium with them, so that such resinous materials are irreversibly flocculated and deposited. The spontaneous coagulation prevents the penetration of the rubber dispersion or equivalent material into the inner layers of the fleece material or even into the surface voids between adjacent fibers during drying and promotes the formation of a surface having the characteristics suitable for the ends to which the present invention is directed. The coagulated material forms spherules which tend to stay at or about one or more surface fiber ends whereby significantly reducing pilling.

Natural rubber, butadiene acrylonitrile rubber and butadiene styrene rubber are preferably employed as binding agents. Additionally, polymerizates and mixtures of polymerizates of acrylic acid-ethyl ester, acrylic acidbutyl ester (acronales), methacrylic acid-ethyl ester methacrylic acid-butyl ester (Plextoles), polyvinyl chloride (Lutofan), polyvinyl acetate (Movilith) may be used.

Preferable fibers comprise natural or synthetic fibers or filaments. These are exemplified by cotton, staple rayon, ramie, nylon, polyester, polyacrylonitrile fibers or mixtures thereof.

The following non-limiting examples are given by way of illustration of certain preferred embodiments of the invention and show possible modification of the process:

EXAMPLE I A random fiber fleece weighing 310 g./m. consisting of crude cotton fibers is, as shown in German Auslegeschrift 1,182,425, impregnated with an aqueous dispersion which is converted into foam, which contains percent solid rubber and 15 percent urea (as a pore former), and as a vulcanization agent, 3 parts sulfur, 1 part zinc salt of diethyldithio carbamic acid, 5 parts zinc oxide and 1 part mercaptobenzimidazole, all parts by weight and taken per 100 parts of solid rubber content.

The fleece, impregnated with the dispersion stirred to a foam, is dried and impregnated for a second time with a mixture of the same composition, which has been thickened to a paste by the addition of 3 percent of the sodium salt of carboxymethyl cellulose. This paste preferentially impregnates the upper layers of the fabric structure. Finally, the bonded fabric material is coated on both sides with an aqueous -percent-solids, foamlike, heat-sensitive natural rubber dispersion which contains, per 100 parts of solid rubber, 2 parts of an alkylaryl sulfonate comprising tetrapropylene benzene sulfonate as a foaming and wetting agent, 1.5 parts of casein as a stabilizing agent, 3 parts of a polyvinylmethyl ether as a heat-sensitizing agent, and as a vulcanizing agent, 10 parts of zinc oxide, 1 part of sulfur, 3 parts of the zinc salt of mercaptobenzothiazole, and 1 part of mercaptobenzimidazole, all parts by weight. This dispersion is foamed mechanically by means of an Oakes mixer prior to application as a coating. After drying, vulcanization is carried out at about 120 C., and subsequently, all pore formers are removed by rinsing in C. warm water, and the material is completely dried. The end product contains, per parts by weight of fibers, about parts by weight of binder, of which 40 g./m. of binder are applied to each side by coating, and weighs about 270 g./m. This decrease in bulk density occurs because the fleece is continuously stretched during impregnation and coating so that the fiber content decreases in weight from 310 g./m. to 120 g./m. and the binding agent accounts for the remainder of the weight.

EXAMPLE II A random fiber fleece substantially the same as in Example I, but consisting of rayon staple fibers, is steeped with a 60 C. warm salt solution which contains 20 percent Glaubers salt and 10 percent urea, then dried and subsequently impregnated with an impregnating mixture thickened to form a paste, as in Example I. Afterwards, a coating is applied to both sides of the fleece, the coating comprising an aqueous 40-percent-solids, heat-sensitive dispersion of a copolymer of 62:38 butadienezacrylonitrile which has the same additives as those given in Example I, and which has been foamed as described in Example I. Finally, the impregnant and coating are vulcanized at 100 C., and all soluble components are washed out in warm water. The final weight of the prod not is about 250 g./m. the fiber proportion, 115 g./m.

EXAMPLE III A random fiber fleece prepared from a mixture of 80 percent bleached cotton and 20 percent ramie is bound together mechanically in a stitching loom and subsequently impregnated with a 60 C. hot salt solution which contains 30 percent Glaubers salt. The material is impregnated with an aqueous 40-percent-solids, heatsensitive rubber dispersion which contains a copolymer of 75:25 butadienezstyrene and corresponding addit ons as in Example I, and afterwards coated on both sides with the same dispersion. After vulcanization if the coating and impregnant at about 100 C., the water-soluble components are washed out in warm water and the mpregnated fleece finally dried. The end product contains, per 100 parts by weight of fibers, about 100 parts by weight of binder, of which 40 g./m. are placed onto each side by coating. I

All of the porous and highly absorbent fleece materials thus prepared have been found to possess excellent abrasion resistance, and furthermore, show no tendency toward pilling after prolonged use in polishing or bufling applications.

COMPARATIVE EXAMPLE Example 2 of US. Pat. 2,719,806 was used as the basis of this comparative example. It will be seen that in this example 16 webs are superposed instead of the 8 webs of the Nottebohm example, and that a butadiene-acrylonitrile copolymer was used here as a binder rather than the polyacrylate of Nottebohm. The foam used here 18 also slightly thinner (8 volumes of air rather than the 5 of Nottebohm patent).

A fiber mixture, consisting of 70 parts by Weight of cotton and 30 parts by weight of spun rayon, is formed into webs having each a thickness of 0.3 mm. and a weight of 19 g./m.

16 such webs weighing 304 g./m. are combined with pressure, heat, and slight longitudinal stretching mm a fleece having a weight of 120 g./ [11.

The fleece is treated on one surface with a foam comprising about 12 volume parts of air and one volume part of a liquid, film-forming binder material contain ng by weight of binder solids and having the following composition:

After drying and solidification of the surface impregnation, which causes a surface deposition of about 6 parts by weight of solid binder material per 100 parts by weight of fibers.

Next, a heavier foam containing about 8 volumes of air per volume of liquid is pressed into the untreated surface of the fleece. This foam is made from a dispersion having the same composition as the dispersion used for the pretreatment. About 40 parts by weight of solid binder material are incorporated into the fleece per 100 parts by weight of fibers.

At this point the procedure followed was according to the instant invention, as follows:

This material was next pased through a salt-bath consisting of a 30% sodium sulphate solution having a temperature of 70 C. Then this material was squeezed until a wet pick-up of and dried.

Subsequently the thus pre-treated fleece was coated on both sides with an aqueous 40% foam-like, heatsensitive natural rubber dispersion as described in Example I. 40 g./m. were applied on each side of the fabric.

The end product contains about parts of the com bined binders from the first impregnation and the coating per 100 parts by weight of fibers.

The end product contains about 40 parts by weight of non-coagulatable binder (internal binder impregnation) and 40 g. of coagulated surface coating applied on each side of the fabric per 100 parts of total product weight.

Besides the rubber emulsions named in the examples, heat-sensittive modified emulsions or dispersions of polyacrylates, copolymers of polyvinyl chloride and polyvinyl acetate and other film-forming agents well known in the art are suitable for the application of the final coating. In addition to natural rubber and the butadiene-styrene copolymers used in the examples, other vulcanizable, elastomeric materials well known in the art may be used as equivalents, provided they may be coagulated at 40- 80 C. with the ether, glycol and siloxane coagulating agents disclosed herein. Alternately, resinous materials well known in the art that coagulate at 40-80 C. without the addition of such ethers, glycols or siloxanes may also be used.

Although the preferred embodiment of the invention comprises utilizing a foamed coating on either side of the fleece material, any semi-continuous or porous coating may be used. For instance, a spot-wise application of the coating material, provided it is applied to yield a coating weight comparable to those disclosed in the example, may be used.

The fleece material employed herein may comprise, in addition to those fibers disclosed herein, any fiber materials which act substantially as full equivalents thereof, such as, for example, theremoplastic fibers of ethylene, propylene, acrylonitirile, acrylic acid, acrylic ester, polyamide, polyester, vinyl halide, vinyl ester, vinyl ether, any copolymers or graft polymers thereof, mixtures of such synthetic fibers with natural fibers and any combination thereof.

According to a particularly preferred aspect of this invention, the non-woven fleece or fabric is impregnated with internal bonding material which is precipitated as lamella, as set forth above; the bonded non-woven fabric is then impregnated with an aqueous salt solution; and then the surface coating with a coagulatable latex is accomplished: It has been found that pre-impregnation with an aqueous salt solution facilitates operations since it has a tendency to repel the coagulatable latex and therefore causes such to remain on the surface of the fabric and to minimize penetration thereof into the fabric body.

Further, it has been found to be most desirable to utilize a coagulatable latex having a higher quantity of rubber material than the quantity of binder impregnated into the fabric.

Thus, there has been discolsed and described a novel method for the preparation of abrasion-resistant, porous, and highly absorbent fleece materials that are resistant to pilling, comprising the application of porous and discontinuous coatings to both sides of fleece material that has been impregnated with a precipitated synthetic resinous compound, according to German Patent 910,960 or German -Auslegesvhrift 1,182,425, or equivalent fleece materials, whereby surface fibers are suificiently bound by such a coating, so that in subsequent polishing or bufling applications, these fibers cannot be worked out to form pills, when any rubbing force is applied.

What is claimed is:

1. A process for producing a repeatedly water-absorbent and abrasion-resistant chamois, leather-like material, which process comprises forming a said fleece with an at least partially dryable liquid form bonding agent composition for the fibers thereof; at least partially drying the impregnated fleece, whereby depositing said bonding agent in the interstices of said fleece joining intersecting fibers with lamella and setting up said bonding agent to an extent SIllTIClfiIlt to substantially maintain the dimensional integrity of said fleece; thereafter applying, to at least both major surfaces of said fleece, a heat sensitive, coagulatable foam-form rubber latex material having a higher solids content than said partially dryable liquid form bonding agent composition under such conditions that said latex remains substantially on the surfaces of said fleece; substantially immediately thereafter heating said latex coating on said surfaces to about 40 to 80 0, whereby spontaneously coagulating said rubber on said surfaces to form a substantially discontinuous film of coagulated rubber material on said surfaces; and vulcanizing said bonding agent and said coagulated rubber.

2. The process as claimed in claim 1 wherein said latex is coagulatable at about 60 C.

3. The process as claimed in claim 1 wherein said rubber is a member of a group consisting of a natural rubber, butadiene-acrylonitrile polymers and butadiene-styrene polymers.

4. The process as claimed in claim 1 wherein said fleece is needled prior to impregnation and wherein said binder and said rubber are substantially simultaneously vulcanized.

5. The process as claimed in claim 1, wherein the liquid bonding agent composition additionally contains a watersoluble material and wherein said water-soluble material is leached out of the bonded fabric after said vulcanization of said bonding agent.

6. The process claimed in claim 1, wherein said rubber latex material has a solids content of about 40%.

References Cited UNITED STATES PATENTS 2,229,061 1/1941 Eustis 1l7-14OX 2,719,795 10/ 1955 Nottebohm 117140X 2,719,806 10/1955 Nottebohm l1714OX 2,774,687 12/1956 Nottebohm et al. 1l7140X WILLIAM D. MARTIN, Primary Examiner H. J. GWINNELL, Assistant Examiner U.S. Cl. X.R.

" UNITED STA'IES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 522 685 Dated ml 13 1221 InvcntorQD Hans Boe It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 5 line 13 "if" should be, of x Col. 5 line 75, "pased" should be passed -2 Col. 6 line 38 "theremopiastic" should be thermoplastic-- C01. 6 line 50 should Be N Col. 6, line 5 9 "discoleed" should be ---disclosed-- Claim l l i ge after "a" insert "watef-absorbent non-woven, textile fleece; impregnating" Signed and sealed this 29th day of Feor-uary 1972.

(SEAL) Attest:

EDWARD M.FLJ:;TCHER,JR. ROBERT GOITSCHALK Attesting Officer Commissioner of Patents 

